The present invention relates to a voice detection and discrimination apparatus in a hearing protection arrangement, and more particularly to a VOX (voice operated transmission/exchange) apparatus, for determining whether an acoustic voice signal is present or absent in a hearing protection arrangement.
The present invention also relates to a method of detecting a voice using the voice detection and discrimination apparatus of the invention in a hearing protection arrangement.
1. Field of Application
Voice activated control is extensively used in communication systems like radio transceivers, intercom systems, recording equipment, etc., and in speech based man-machine-interfaces.
This invention is intended for use in noisy environments, e.g. in environments where some source of acoustic noise is predominant, making it difficult to hear or where damage to the hearing could be at risk. In such environments there could for example be heavy operating machinery or loud vehicle traffic nearby. In other environment there may be large crowds of people. For example in sports stadiums, such as football arenas or the like, where a lot of noise is generated by the audience.
In particular, the primary application for the invention is in situations where it is desirable for people to use a hearing protection arrangement, while still requiring some means of communicating, e.g. to speak with other people or to give commands to voice operated equipment.
2. Prior Art
Present day devices intended to pick up speech from a person in a very noisy environment as a basis for voice detection represent a technological challenge and take several forms. Common types include;
A microphone in close proximity to the mouth, carried on a microphone boom. The microphone is made with a characteristic emphasising the near field from the mouth. This type is often called xe2x80x9cnoise cancellingxe2x80x9d.
A vibration pickup in contact with the throat, picking up the vibrations of the vocal cord.
A vibration pickup in contact with the wall of the meatus, the outer ear canal, picking up the vibrations of the tissue in the head.
A similar pickup in contact with the cheek-bone.
A microphone picking up the sound in an enclosed space in the inner portion of the meatus.
Detection of voice is based on several techniques:
Measurement of signal strength of a band-pass filtered microphone/vibration pick-up signal,
Advanced signal processing on signal picked up by a microphone (A survey of methods are found in Bishnu S. Atal, Lawrence R. Rabiner: xe2x80x9cA Pattern Recognition Approach to Voice-Unvoiced-Silence Classification with Applications to Speech Recognitionxe2x80x9d, IEEE Transactions on Acoustics, Speech and Signal Processing, Vol. ASSP-24, No. 3, June 1976, pp 209-212.
Present day devices often fail to work properly in noisy environments. The following types of errors often take place:
The device is not activated by normal voice
Noise falsely activates the device in case of no speech
It is an object of the present invention to provide a voice detection and discrimination apparatus providing much improved performance in noisy environments.
It is a further object of the invention to provide a VOX (voice operated transmission/exchange) apparatus which is capable of detecting and discriminating a voice in a noisy environment.
It is yet an object of the invention to provide a voice detection and discrimination apparatus with improved voice detection capability and which has a reduced false activation due to acoustic noise.
In particular, it is a further object of the invention to provide a VOX (voice operated transmission/exchange) apparatus suitable for use with electronic communication systems being used in noisy environments.
It is also an object of the present invention to provide a method of detecting a voice for the control of a voice operated system, by employing an ear terminal element intended also for protecting the hearing function by providing acoustic attenuation.
According to the invention, these objectives are achieved in a voice detection and discrimination apparatus for controlling a voice operated system comprising a protective ear terminal element for protecting the ear by providing acoustic attenuation. An inner electroacoustic transducer element on an inner side of the ear terminal element detects a first acoustic field and provides a first electronic signal representing said first acoustic field. An outer electroacoustic transducer element on an outer side of the ear terminal element detects a second acoustic field and provides a second electronic signal representing said second acoustic field. An electronics unit is connected with said electroacoustic transducer elements. The electronics unit comprises first comparison means for comparison of said first and second electronic signals in order to obtain the difference between said two electronic signals. The electronics unit also comprises second comparison means for comparing said difference with given criteria. Output means connected to said electronics unit provides an output signal depending on said second comparison. The output signal is used as an input signal to the voice operated system.
According to the invention the objectives are also achieved with a corresponding method of detecting a persons own voice and for controlling a voice operated system, employing an ear terminal element for protecting the ear by providing acoustic attenuation. The method comprises the following steps: The acoustic signal strength on the inner side of said ear terminal element is detected using a first electroacoustic transducer element. The acoustic signal strength on the outer side of the ear terminal element is detected using a second electroacoustic transducer element. A difference value representing the difference in the acoustic signal strength between the inner and outer side of the ear terminal element is obtained. Using the value representing the obtained difference and given criteria, it is decided if a voice is present. An output signal depending on the decision is provided using an output means. The output signal is used as an input to a voice operated system.
Further preferable embodiments of the invention are defined in the independent claims.